4 mile run/walk

Today we went to the bike path to run 4 miles. It was kind of humid today which made the run very difficult. Felt like someone was pushing me in my chest trying to slow me down the entire time. Sometime after mile 3, I was taking my normal stride and when my left foot came forward I just started walking. It wasnt a conscious decision.....my body just had enough. I walked for about 5 minutes and then was able to jog it back to work.